I'm trying to figure out how I should be using the fix version and affects version fields. I'm also curious which fields the different widgets use. For example, I see the roadmap widget uses the fix version field.
Affects version = where you found the problem
Fix version = where you plan to fix it, or where it has been fixed (depending on your process)
Affects version is not heavily used - it's very useful for what it does, but there's not a huge amount of useful reporting you can do on it beyond the basic "where did it break" or "how many bugs did this version contain" questions.
Fix versions however, is for planning, releases, tracking velocity, monitoring progress, as well as it's core "it was fixed in" intent, and others, so it's used in a lot more of the widgets and reports. Try Greenhopper/Agile on a project where it's disabled, and you'll find 90% of it doesn't do much!
Assuming fixed version numbers are greater than the affected versions within in the same ticket (for cases when the fix version is changed to later releases) can the affected version be an accurate indicator that a change has been made to the fixed version? I'm attemtping to bulid a query shows the number of tickets that were changed from one fixed version to another so far this is the best indicator I have.